The International Astronomical Union (IAU) is announcing that the names Kerberos and Styx have officially been recognised for the fourth and fifth moons of Pluto, which were discovered in 2011 and 2012. The names were submitted to the IAU by the leader of the team responsible for the discovery, who had called for the help of the general public in an open contest that attracted a substantial number of participants.

The IAU is pleased to announce that today it has officially recognised the names Kerberos and Styx for the fourth and fifth moons of Pluto respectively (formerly known as P4 and P5). These names were backed by voters in a recently held popular contest, aimed at allowing the public to suggest names for the two recently discovered moons of the most famous dwarf planet in the Solar System.

The new moons were discovered in 2011 and 2012, during observations of the Pluto system made with the NASA/ESA Hubble Space Telescope Wide Field Camera 3, and increasing the number of known Pluto moons to five. Kerberos lies between the orbits of Nix and Hydra, two bigger moons discovered by Hubble in 2005, and Styx lies between Charon, the innermost and biggest moon, and Nix. Both have circular orbits assumed to be in the plane of the other satellites in the system. Kerberos has an estimated diameter of 13 to 34 kilometres, and Styx is thought to be irregular in shape and is 10 to 25 kilometres across.

The IAU acts as the arbiter of the naming process of celestial bodies, and is advised and supported by astronomers active in different fields. On discovery, astronomical objects receive unambiguous and official catalogue designations. When common names are assigned, the IAU rules ensure that the names work across different languages and cultures in order to support collaborative worldwide research and avoid confusion.

After the discovery, the leader of the research team, Mark Showalter (SETI Institute), decided to call for a public vote to suggest names for the two objects. To be consistent with the names of the other Pluto satellites, the names had to be picked from classical mythology, in particular with reference to the underworld — the realm where the souls of the deceased go in the afterlife. The contest concluded with the proposed names Vulcan, Cerberus and Styx ranking first, second and third respectively. Showalter submitted Vulcan and Cerberus to the IAU where the Working Group for Planetary System Nomenclature (WGPSN) and the Committee on Small Body Nomenclature (WGSBN) discussed the names for approval.

However, the name Vulcan had already been used for a hypothetical planet between Mercury and the Sun. Although this planet was found not to exist, the term “vulcanoid” remains attached to any asteroid existing inside the orbit of Mercury, and the name Vulcan could not be accepted for one of Pluto’s satellites (also, Vulcan does not fit into the underworld mythological scheme). Instead the third most popular name was chosen — Styx, the name of the goddess who ruled over the underworld river, also called the Styx.

After a final deliberation, the IAU Working Group for Planetary System Nomenclature and the IAU Committee on Small Body Nomenclature, in charge of naming dwarf planets and their systems, agreed to change Cerberus to Kerberos — the Greek spelling of the word, to avoid confusion with an asteroid called 1865 Cerberus. According to mythology, Cerberus — or Kerberos in Greek — was a many-headed dog that guarded the entrance to the underworld.

The IAU wholeheartedly welcomes the public’s interest in recent discoveries, and continues to stress the importance of having a unified naming procedure following certain rules, such as involving the IAU as early as possible, and making the process open and free to all. Read more about the naming of astronomical objects here. The process of possibly giving public names to exoplanets (see iau1301), and more generally to yet-to-be discovered Solar System planets and to planetary satellites, is currently under review by the new IAU Executive Committee Task Group Public Naming of Planets and Planetary Satellites.

moorouge

Mmm - I may be wrong, but I always thought that Styx was the Underworld river, not a goddess.

Robert Pearlman

Styx was the name of the river and the goddess. From Wikipedia:

Styx was also the name of the daughter of Oceanus and Tethys. She was wife to Pallas and bore him Zelus, Nike, Kratos and Bia (and sometimes Eos). Styx supported Zeus in the Titanomachy where she was the first to rush to his aid. For this reason her name was given the honor of being a binding oath for the gods.

onesmallstep

Damn! I was hoping for Bambi and Thumper. I guess there aren't many Disney fans in the IAU.

Blackarrow

Hmmm...a body orbiting the sun surrounded by a family of five moons. If Pluto doesn't deserve to be called a planet, I'm a monkey's uncle.

Robert Pearlman

And so are you saying every minor body with moons is a planet? That asteroid that flew by Earth not too long ago had a moon orbiting it, was that a planetary flyby?

Playing devil's advocate, but having moons (of any quantity) clearly cannot be the sole qualifier for planethood.

Blackarrow

Robert, you little devil's advocate! I didn't know the space-rock which flew past us recently was accompanied by a space-pebble, but that's hardly comparable with a substantial spherical planetary body with a retinue of five moons (plus those yet to be discovered by Hubble or New Horizons).

Pluto has been known for 83 years, and accepted for most of that time as a planet. I acknowledge that on strictly logical, hard-nosed astronomical criteria Pluto cannot be distinguished from several other similar Kuiper Belt objects, but the debate should make some allowance for more human considerations.

We think of the Solar System as the sun's "family." Venus is our "sister world." Jupiter is the "king of the planets." This is what ordinary people think. We anthropomorphize the planets. That is why millions of people followed the journey of the Voyagers through the Solar System, and why so many people were awe-struck by pictures of the surprisingly Earth-like blue planet Neptune at the edge of the sun's realm.

No, it's not really logical, but there should be room for human sentiment in the Pluto debate. An exception should have been made for Pluto, if for no better reason than that we knew of Planet Pluto for nearly eight decades.

Robert Pearlman

quote:Originally posted by Blackarrow:That is why millions of people followed the journey of the Voyagers through the Solar System...

This doesn't help your position, as if Pluto is not a planet, than the Voyager probes did indeed explore all the planets in our solar system.

canyon42

Well, not exactly, Robert. The Voyagers never visited Mercury, Venus, or Mars. But your point stands.

The problem with including human "sentiment" in classification schemes is that it will likely lead to only more confusion in the future. Sure, for us, we "know" that Pluto is a planet, because that's what we learned growing up. There wasn't any information to the contrary at that point, but now there is. Not only is Pluto much smaller than believed even back in the 60s and 70s, we now have evidence that there are multiple bodies in the outer solar system that are just as big and bigger — and no reason now that we've found those to believe that there won't be many, many more discovered in the future.

So yeah, we could give Pluto the benefit of a grandfather clause, which might make our generation feel better somehow, but think logically where that could lead. Suppose 50 years from now the Kuiper Belt is much better mapped and we have found dozens — or hundreds — or THOUSANDS — of bodies equivalent to or larger than Pluto. What are we going to teach the children of THAT generation? "There are nine planets, plus a whole bunch of dwarf planets." "But (some/lots/a few) of those dwarf planets are bigger than Pluto. Why does IT get to be a planet but none of the rest do?" "Because, my dear, we decided to keep calling it a planet because... well, because that's what people were used to calling it." "So... Pluto isn't really any different from any of those other dwarf planets, but we call it a planet... even though it really isn't."

Do we really want kids to learn that that is how science works? Or do we want them to learn that science depends on information, and as that information gets more refined or superseded by better information we revise our beliefs and ideas?

Blackarrow

And why do we still call the flat, dry volcanic plains of the Moon "seas"? Because that's what we used to call them back in the days when we thought they were full of water.

My first space book ("The Golden Book of Astronomy" signed 'From Daddy, 9th May, 1961') acknowledges that at least three moons in the Solar System are bigger than Pluto, yet I was never aware, growing up as a space-nut, of any debate about stripping Pluto of its status as a planet. Size isn't necessarily the issue.

If Canyon42 wants to strip all human sentiment out of astronomical classification systems, lets just give the planets numbers, replacing "Mercury" with "Planet 1", "Venus" with "Planet 2" and so on. Let's not name moons and asteroids after poets, writers, sculptors, explorers or deities. Numbers will do. Names might give children the silly notion that identifying objects in space is carried out on sentimental rather than scientific grounds.

canyon42

Wow.

Call it whatever you like, man. Doesn't make any difference to it. And incidentally, "naming" an object is most assuredly not the same thing as "classifying" it. Just for the record.

Robert Pearlman

quote:Originally posted by canyon42:Well, not exactly, Robert. The Voyagers never visited Mercury, Venus, or Mars. But your point stands.

Oops, forgot the word "outer" before planets.

And just like admitting that error, the great thing about science is that it is open to correction and change. It doesn't follow a bible written in stone; classifications can (and do) change as more is observed and learned about a topic of study.

moorouge

Putting my tongue firmly in my cheek, perhaps one should call them all 'planetoids'?